Electrical stimulation of the septal-hippocampal pathway increases the turnover rate of acetylcholine in the hippocampus, whereas fimbrial lesions decrease the turnover rate. The indirectly acting dopaminergic and noradrenergic agonists, amphetamine and nomifensin, increase the turnover rate of acetylcholine in the cortex and hippocampus. The excitatory effect of both drugs is blocked by intraseptal phenoxybenzamine. The directly-acting dopamine agonist, apomorphine, decreases the acetylcholine turnover rate in the hippocampus. The dopamine blocking agent haloperidol when injected directly into the septim increases the turnover rate of acetylcholine in the hippocampus. Injection of 6-hyroxydopamine into the septum or into Area A10 also increases the turnover rate of acetylcholine in the hippocampus. The directly-acting GABA agonist, muscimol, when given intraseptally decreases the turnover rate of acetylcholine in the hippocampus. Bicuculline is without effect when given directly into the septum.